Biologists have discovered a new species of insects

Neuroterus valhalla is a newly described species of cynipid gall wasp that was discovered in the branches of a live oak tree near the Rice University graduate student’s Valhalla pub. Credit: Miles Chang/Smithsonian NMNH

Its name sounds legendary, but the newly discovered insect Neuroterus (noo-ROH’-teh-rus) Valhalla doesn’t look or act the part. It is barely a millimeter tall and spends 11 months of the year locked in a cellar.

N. valhalla has the notable advantage of being the first insect species to be described along with its entire genome sequenced, and the Rice University researchers who discovered it are preparing to see how the tiny, non-stinging wasps might have been affected by the historic Houston February 2021 freeze.

N. Valhalla described in a paper published this month in systematic entomology. Its name is in homage to the place it was discovered: outside the Valhalla pub for Rice alumni.

Graduate student Pedro Brandao Dias, lead author of the paper, who first collected N. Valhalla from the branches of a huge live oak tree near the campus bar in Spring 2018.

Brandao, who is Brazilian, had never seen an oak before visiting Rice in 2015 for an undergraduate research fellowship in the lab of evolutionary biologist Scott Egan, corresponding author of the study. Brandão returned to Egan’s group in 2018 for graduate studies, and although Brandão’s initial research focuses on using ecological DNA to detect endangered or invasive species, everyone in the lab applies every spring to study insects of the Cynipidae family. Known as gall wasps, they are a favorite of the Egan group because they can be collected from the live oak trees that cover Rice’s 300-acre campus. In Egan’s eight years at Rice, his lab has discovered at least a number of new species of gall wasps, or the predators that attack them.

“At Rice, we emphasize learning by doing,” Egan said. “In my lab, undergraduate and graduate students participate in the process of experiential learning by studying biologically diverse ecosystems on live oaks just outside our front door. With some patience and a magnifying glass, the discoveries are endless.”

N. valhalla and other gall wasps trick the host tree into feeding and harboring their young. Wasps lay a biochemical cocktail with their eggs. The chemicals convince the tree to form a crypt, or gallbladder, around the egg. The gallbladder protects the egg and nourishes the larvae that hatch from it.

There are approximately 1,000 known species of gall wasps. Some appear as spherical brown balls that form on the underside of oak leaves. Others form beams within the branches and others on the blossoms of trees, where Brandau first collected N. Valhalla.

“Once they appear, they only live three or four days,” Brandau said of the little bugs. “They don’t eat. Their only goal is to mate and lay eggs.”

One reason it took nearly four years for the new species to be described is that N. valhalla – like many other larks – lays eggs twice a year. It took some time to discover where N. valhalla laid her eggs in her alternating generation.

Brandau and his colleagues first observed N. valhalla on the large tree outside of Valhalla while they were collecting live oak flowers, or catkins, in late February and early March of 2018. They were looking for another type of galliere known to form beams on flowers. When DNA tests revealed two species, the researchers took a closer look at their catch and noticed some small, light-colored legged insects.

Brandau said of N. Valhalla: “They lay their eggs in cats that develop.” “They develop in tannins on the flowers, and then they appear. That happens in March. But the flowers repeat once a year, and by the time they appear, there are no more flowers to lay eggs on so they have to lay the eggs on a different napkin.”

Biologists have discovered a new species of insects

Artist’s illustration of the life cycle of Neuroterus valhalla, a cynipid gall wasp that uses chemicals to induce live oaks to grow protective crypts or balls around their eggs. females give birth n. Valhalla (A and D2) twice a year in alternating generations in different locations on the trees. One generation appears in February or March, lays eggs in live oak blossoms (B) and spurs balls (C1) where adults will emerge within 2-3 weeks. These eggs lay in the branching stem ganglia (E), resulting in the induction of globules (F1) from which adults will emerge after 11 months. Ecologists discovered N. valhalla at Rice University, and have not yet found a male member of the species (center). Credit: Barbara Rossi

Egan said the alternating generations of galleries have often been confused with new genres in the past. Genomic testing combined with detailed observations in nature was crucial to determining that N. valhalla was a unique species. Knowing where the bugs have gone in their alternate generation takes luck and hard work.

Kelly Weinersmith, assistant professor of biosciences, and collaborators at the University of Iowa got their lucky shot in 2019. Weinersmith sampled live Florida oak plants that differ from the cedar trees where N. valhalla was found. Weinersmith sent samples from the Florida expedition to Iowa collaborators Andrew Forbes and Anna Ward, who noticed two distinct species of wasps emerging from cryptic gallbladder swellings at branch intersections. DNA tests showed that the unknown wasp is the lost generation of N. valhalla.

“To make sure where they are going after they have left the flowers, I conducted an experiment where we gave the wasps a range of different tissues from the tree and observed them,” Brandau said. The idea was to watch the N. valhalla that had just emerged from the katkin vaults in Rice and catch them laying their eggs on a different part of the plant.

With COVID-19 restrictions limiting the number of people who could be in labs on campus in early 2020, much of the work fell on Rice student Camilla Vinson, who lived on campus at Brown College.

“We were going out together and collecting catechin balls and tissues for behavioral tests in Petri dishes, but she had to go every day to the lab to see if any insects came up,” Brandau said. Brandau said Vinson cataloged and collected samples of wasps that emerged from cats and “we did an observational experiment where we put the bugs in a petri dish with a set of tissues and then watched them to see where they went.”

“Because this was during COVID,” he said, “I took some of them home and put them in a microscope and took pictures with my phone.”

The team confirmed the Petri dish results by examining the trees where they had previously collected N. valhalla. They found both holes emerging from ancient crypts and more than a dozen birds still containing N. valhalla larvae.

The generation of N. valhalla that hatches into live oaks goes from eggs to fully formed insects within 2-3 weeks, Brandau said. The cycle takes 11 months for the generation growing inside the branches.

“If they come out at the wrong time, and there are no flowers around, they cannot lay their eggs and die,” Brandau said. “They have to get out on time for the tree to bloom.”

The trees bloom at different times from year to year, and it is not clear how wasps coordinate their appearance with flowering. Vinson was the first to ask the question of how N. valhalla was affected by the winter storm in February 2021, which caused record cold temperatures and delayed flowering of live oaks across Houston.

“The day the freezing happened, I asked Pedro, ‘Is this going to spoil when they come out or even their ability to reproduce?”‘ she recalls. Brandau circulated the question to an international group of wasp researchers. It’s worth following, so Vinson decided to address it in her senior thesis, she said, as part of a larger question about how climate change might affect specialized insects like wasps.

“Our wasps live on live oak trees from the southern United States all the way to Mexico,” Vinson said. “These environments are not used to the kinds of temperatures we saw last February. And these kinds of freezes are likely to happen more and more with climate change.

“The big question is, ‘Will these populations be at risk, or can they adapt quickly? Do they have strategies that align well with the changing climate? ”

The Crypt-Keeper wasp has been found parasitizing multiple species of gall wasps

more information:
Pedro FP Brandão‐Dias et al, Description of genome-era biodiversity: a new species of near-Antarctic wasp Cynipidae and its genome, systematic entomology (2022). DOI: 10.1111 / syen.12521

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